It seems neither HD supports GL 4.0, although Geeks3D reported something quite differently.
HD 2500 and 4000 should have the same architecture, and I couldn't find traces of tessellation shaders
The results on HD 2500 and HD 4000 are identical. Is it possible that only 2696 has GL 4.0 support that is removed from the following revisions?

Originally Posted by Alfonse Reinheart

Did you look at what extensions were missing from the 3.0/3.1/3.3 cases for the HD2500?

Of course! But I have to revise my extension viewer considering GL 3.0. It's an old code rely on the first implementation in NV drivers. That's why I changed some numbers in the previous post. Thank you for the question! It makes me check "my understanding" of GL versions. I'll revise it completely.

Considering GL 3.1, GL_ARB_texture_buffer_object is not supported in 8.15.10.2761 drivers, and GL_ARB_shading_language_include, GL_ARB_texture_swizzle from GL 3.3.

I've got the point! Take a look at drivers versions:
First GL 4.0 support at 9.17.10.2729
Another test is done with 9.17.10.2792

Those are not Win7 drivers. That's the point. The mystery is solved.
OpenGL 4.0 is supported on Win8, but not on Win7!

Although I'm a little bit disappointed by this discovery, it proves the future is bright for the OpenGL on Win8.
Despite all concerns Windows is and probably will be the best development platform for the OpenGL.

P.S. Thanks mhagain! You could update your driver to take a look whether there is any new extension, since it is not the latest one. And even if there are no updates, some bugs are probably fixed.

I will try it tomorrow. I remember that I had some problems when I tried to install some of those drivers, but I'll try again. Last week I was a witness that Intel graphics driver cannot install at first, but it succeeds after some of the Windows updates. I'll report the results here. Thanks!

GL_ARB_texture_swizzle and GL_ARB_texture_buffer_object are supported in the 8.15.10.2696 drivers, though they aren't listed in the extension string. I became a little suspicious after the latest driver for my AMD FirePro card also didn't list GL_ARB_texture_swizzle but claimed GL4.2 support and properly supported it, so I decided to recheck the HD4000. The shader with samplerBuffer compiled without incident, and the glTexBuffer API entry point was found. Swizzling also works properly ( glTexParameter(GL_TEXTURE_2D, GL_TEXTURE_SWIZZLE_RGBA) ).

However, the noperspective keyword throws a syntax error in a shader in an interface block, and one of my #define's appears to be broken with the paste operator (##). Even with these bugs, the situation is certainly better than any Intel GL driver I recall.